1. Field of the Invention
The present invention relates, in general, to flat fluorescent lamps used as backlight units in display devices and, more particularly, to a flat fluorescent lamp for display devices, which has an improved electrode structure for plasma discharge, thus being efficiently operated using a low voltage and having high optical efficiency.
2. Description of the Related Art
Generally, display devices have been classified into two types: emissive display devices and non-emissive display devices, according to their ability to emit light. Liquid crystal displays (LCD) widely used as flat panel display devices in recent years are examples of non-emissive display devices that cannot emit light themselves, so that the LCDs must be backed with backlight units (BLU).
In recent years, flat fluorescent lamps (FFL) have been preferably and widely used as the BLUs for LCDs. The FFLs may be configured as internal electrode fluorescent lamps (IEFL) having internal electrodes for plasma discharge as shown in FIG. 1, or external electrode fluorescent lamps (EEFL) having external electrodes for plasma discharge as shown in FIG. 2.
As illustrated in FIGS. 1 and 2, a conventional FFL comprises a lamp body 100a, 100b fabricated with an upper plate 101a, 101b and a lower plate 102a, 102b which are closely integrated along their edges into a single sealed body. Furthermore, a channel 103a, 103b is formed on the lamp body 100a, 100b as a continuous long channel having a serpentine shape so that, when the upper plate 101a, 101b is integrated with the lower plate 102a, 102b into a lamp body 100a, 100b, the serpentine channel 103a, 103b defines a plasma discharge space in the FFL. The FFL further comprises electrodes 104a, 104b for plasma discharge provided at opposite ends of the serpentine channel 103a, 103b. Inert gas including mercury vapor is contained in the serpentine channel 103a, 103b to cause plasma discharge in the plasma discharge space of the FFL. Furthermore, a fluorescent material is coated onto the inner surface of the serpentine channel 103a, 103b, thus forming a fluorescent layer to emit light due to the energy of the excited gas in the channel 103a, 103b. 
The electrodes of the conventional FFLs may be provided at opposite ends of the serpentine channel 103a by inserting the electrodes 104a into the ends, thus providing an IEFL as shown in FIG. 1, or may be provided on an external surface of the lower plate 102b at predetermined positions corresponding to the opposite ends of the channel 103b by attaching an electrode material to the external surface, thus providing an EEFL as shown in FIG. 2. However, the electrodes 104a provided at opposite ends of the channel 103a of the IEFL are problematic in that it is difficult to insert the electrodes 104a into and fix them in the ends of the channel 103a during an FFL manufacturing process. In an effort to overcome the above-mentioned problems caused in conventional IEFLs, and to avoid direct interaction between the electrodes and the plasma in the serpentine channel, and, furthermore, to accomplish the requirements of providing a large FFL system by integrating a plurality of FFLs into a single system through a tiling method, the EEFLs as illustrated in FIG. 2 have been actively studied and developed.
However, although the above-mentioned serpentine channel defining the long plasma discharge space of an FFL with electrodes provided at opposite ends of the channel provides of the FFL with high optical power and high optical efficiency, the long plasma discharge space undesirably causes a problem in that the plasma discharge start voltage and the plasma discharge drive voltage are undesirably increased. This increases the electric power consumption of the FFL due to the intrinsic properties of the FFL having low optical efficiency relative to the high voltage applied to the electrodes, and reduces both the expected life span and the operational reliability of the FFL, and retards the commencement of operation of the FFL.
Generally, in an FFL, the plasma discharge efficiency and the drive voltage relative to a distance between plasma discharge electrodes vary in inverse proportion to each other. Thus, a reduction in the drive voltage for the FFL may be accomplished by reducing the distance between the electrodes. However, the reduction in the interelectrode distance in the FFL undesirably degrades the plasma discharge efficiency and reduces the size of the FFL.